Height measuring devices for measuring the heights of articles with high precision by using a light source and a camera have been conventionally known (for example, see Japanese Unexamined Patent Application, Publication No. 2000-356510).
When there are a plurality of height measurement points at separate positions in the horizontal direction, and the heights at the measurement points are to be measured with high precision, it is necessary to provide the same number of measurement instruments as the number of measurement points or to move, by using a highly-precise movement device, a measurement instrument to the measurement points for measurement.